The invention concerns the field of CAN (Controller Area Network) sensing devices.
The invention concerns the field of CAN sensing devices.
CAN networks are widely used in the vehicle industry, from airplanes to trains and automotive vehicles. There is a common need to monitor the activity on the CAN network of a given vehicle. For warranty and reliability reasons, third parties have designed wireless CAN network sensors.
A classical CAN network sensor comprises a clamp-like portion, which is designed to put each of the pair of CAN cables in vicinity with a respective electric component, so as to generate two respective capacities. The analogue signal which is sensed at the respective capacities when the CAN cables are received is driven towards a remote processing unit, which reconstitutes the signal on the CAN cables from the sensed analogue signal.
While seemingly simple on paper, the manufacturing of wireless CAN network sensors poses great challenges. Inductive sensing was first envisioned, due to its easier design. However, it is more sensitive to surrounding noise, and proved to be unfit in real-life vehicle environment, which are extremely noisy.
The use of capacity sensing thus constituted a first major breakthrough in the wireless CAN sensor industrialization. In order to overcome the low energy yield of the capacitive technology, the first wireless CAN sensors were designed to offer the biggest capacitive matching surface available for the CAN cables. Since sensors surrounding the cables were hard to manufacture and use, long and flat sensors were used, in order to improve the sensed amplitude.
The resulting sensors are bulky and unpractical to use. Indeed, the CAN cables in vehicles are usually located in somewhat remote locations, and are tightly twisted together and with other cables, forming complex vehicle harnesses. Since the sensors show great lengths in order to maximize the amplitude of the sensed signal, it is necessary to untwist long portions of twisted CAN cables, resulting in slow operation and damages to the vehicle CAN cables, as well as the other cables in the vehicle harness.